The invention relates to a method and an apparatus by which a thick fibrous material web can be threaded into a winder. The invention is especially directed to winding thick fibrous material webs, e.g. pulp webs. The thickness of said thick fibrous material webs amounts to more than 0.5 mm and especially more than 0.7 mm.
Winders or reels are used to wind a fibrous material web and to transport, store or supply it to further processing in said wound state. During winding the fibrous material web is wound around a core which is rotated and around which the fibrous material web is wound.
Such winder or reel is frequently employed together with a cutting device in which the fibrous material web is cut to the width to be supplied, wherein in this case usually cores cut to length corresponding to the web cuts' widths are used onto which the web cuts simultaneously arriving from the cutting means are synchronously wound in the winder.
The cores are very quickly fully wound especially in the case of thick fibrous material webs so that the cores have to be exchanged. After the exchange the web cuts or else the entire web has to be joined to the cores as winding starts so that then winding can be performed in the usual way by rotating the core or the cores.
From the state of the art according to U.S. Pat. No. 7,458,539 a winder is known in which a fibrous material web is to be wound around a core located on two bearer drums in a winding bed and forming respective nips with the two bearer drums.
The web to be wound is guided with its leading edge ahead coming from below through one of the nips to the core and there the leading end of the web is bonded to the core by a double-sided adhesive tape. To this end, a scraper scrapes the web leaving the nip from the bearer drum, the scraper element then making a tilting movement so as to press by a surface the leading end of the web against the core at the position where the adhesive tape is provided. For this solution an adhesive tape is required, however.
Furthermore, a state of the art is known which does not require an adhesive bonding of the leading end. A core is supported on two bearer drums in a winding bed and forms respective nips with the two rollers. The web to be wound is guided from above through the first one of the two nips, moves beneath the core and then passes the other nip. The leading end of the web leaving the nip is caught by a baffle plate and moves along the baffle plate until the latter is covered by the leading end of the web on the side where the first nip is provided.
The baffle plate is now swiveled in the direction of the first nip so that a longitudinal edge of the baffle plate is moved toward the first nip. The projecting leading end of the web is folded or bent about the longitudinal edge of the plate so that the web is adjacent to both sides of the baffle plate, a web tail being formed which extends away from the longitudinal edge of the baffle plate. The baffle plate now introduces the portion of the web folded around the longitudinal edge into the nip. A suitably shaped guide member may assist this insertion. Upon further rotation the web end is pressed against the core by the following web so that the first winding is completed. After several revolutions the web end is sufficiently secured to the core so that the winding operation is performed in the usual way, e.g. with the aid of a press roll biasing the core against the bearer drums.
The threading technology according to this state of the art forms a thickness step of three layers of fibrous material web where the web for the first time overlaps its end inserted in the nip. It has turned out that especially in the case of thicker fibrous material webs at a position corresponding to this point, breaks in the web can occur even later in the wound product. Hereinafter the terms of fibrous material web and web will be used synonymously for the fibrous material web.